Hematologic Assessment A normochromic normocytic anemia is present in about two thirds of patients at diagnosis. In part, anemia is related to the hypervolemia caused by the increase in plasma volume because of monoclonal protein production. Rouleaux formation is a common finding on peripheral blood smears. The leukocyte count can be normal, although about one third of patients have leukopenia. Relative lymphocytosis is usually present. If lymphocyte subsets are examined, a reduction in CD4+ (helper) and an increase in CD8+ (suppressor-cytotoxic) blood lymphocytes can be noted. Defects in the proliferative responses of lymphocytes to mitogens or antigens are explained by the large portion of B cells in MM that originate from the malignant stem cell clone. Few mature plasma cells are seen in the circulation except at the terminal phase of the disease, but the covert presence of the malignant B cell clone can be unmasked by the laboratory use of monoclonal antibodies (MAbs) or by transforming agents such as phorbol esters. In rare cases, in the terminal stages, plasmablasts and proplasmacytes may amount to 50% of the leukocytes in the peripheral blood.

Bleeding is common. Platelet abnormalities, impaired aggregation of platelets, and interference with platelet function by the abnormal monoclonal protein contribute to bleeding. Inhibitors of coagulation factors and thrombocytopenia from marrow infiltration of plasma cells or chemotherapy may also contribute to bleeding. Some patients have a tendency toward thrombosis, which may manifest as a shortened coagulation time and increased levels of fibrinogen and factor VIII.

Diagnosis of MM, however, depends on the demonstration of an increased number (>10%) of plasma cells in a bone mar row aspirate (Fig. 1) and/or biopsy and supporting laboratory results. Cytogenetic analysis or fluorescence in situ hybridization (FISH) of bone marrow aspirate is recommended.

Fig1. Myeloma cells in a bone marrow aspirate. (From Bauer JD: Clinical laboratory methods, ed 9, St Louis, 1982, Mosby.)

Bence Jones Proteins

Bence Jones proteins have been important diagnostic markers for MM since the mid-19th century (see later, “Bence Jones Protein Screening Procedure”). In about 10% of MM patients, only BJ proteins are produced, with no complete IgM, IgG, or IgA. BJ proteins are single-peptide chains with a molecular weight of 20 to 22 kkDa, but dimerization occurs spontaneously to form molecules of 40 to 44 kDa.

Bence Jones proteins are monoclonal κ or λ immunoglobulin free light chains (FLCs) not attached to the heavy-chain portion of the immunoglobulin molecule. BJ proteins are seen in two types of syndromes:

• With a typical monoclonal gammopathy

 • In free LCD

Serum concentrations of FLCs depend on the balance between production by plasma cells and their precursors and on renal clearance. If there is increased polyclonal immunoglobulin production and/or renal impairment, both κ and λ FLC concentrations can increase by 30% to 40%. Serum FLC tests have been assuming an increasing role in the detection and monitoring of monoclonal gammopathies. Serum FLCs have a short half-life in the blood (κ, 2 to 4 hours; λ, 3 to 6 hours), compared with 21 days for IgG molecules. FLC concentrations allow more rapid assessment of the effects of chemotherapy than monoclonal IgG levels.

Very small amounts of BJ proteins in serum can be associated with significant clinical problems, especially pathologic renal changes. FLCs filter through the glomeruli almost without obstruction because of their small molecular size and accumulate in the tubules. Renal impairment can result from the toxicity of FLCs. Pathologic changes can range from relatively benign tubular proteinuria to ARF or amyloidosis.

BJ proteins can be detected in serum, urine, or both. The level of monoclonal light chains in serum or urine is related to filtration, resorption, or catabolism of the protein by the kidneys. During the early stages of renal disease, when the kidneys are only mildly affected, excretion and reabsorption continue normally, but only partial catabolism occurs. At this point, BJ proteins may be detected in the serum but not in the urine. Progressive renal involvement impairs reabsorption, and diminished reabsorption with decreased catabolism results in FLCs in serum and urine. Later, as resorption is totally blocked, FLCs are present in urine only. In terminal stages of renal dis ease, uremia occurs, renal clearance is affected, and BJ proteins again appear in the serum.

BJ proteins are unusual in their response to heating. They are soluble at room temperature, become insoluble (forms a precipitate around 60° C to 70° C, and then dissolves at 100° C). This pattern reverses when the temperature is lowered, which is unique to BJ protein.

Serologically, all BJ proteins are not identical, although there are κ and λ types. BJ proteins will react with antisera to the λ chains of IgG and λ chains react with antisera to BJ protein.

Approximately 80% of patients with MM produce intact immunoglobulin monoclonal proteins, of which 46% have excess monoclonal FLCs in the urine by immunofixation electrophoresis. Serum protein electrophoresis is positive less often because of low serum concentrations of FLCs. From 3% to 4% of MM patients have nonsecretory disease. These patients have no detectable monoclonal proteins with serum and urine electrophoretic testing because their tumor cells produce small amounts of monoclonal protein. Their FLC concentrations are below the sensitivity of serum electrophoretic tests and below the threshold for clearance into the urine. These patients can be monitored by serum FLC tests rather than by repeated bone marrow biopsies or whole-body scans.

Free Light Chains

Free light chains are incorporated into immunoglobulin molecules during B lymphocyte development and expressed initially on the surface of immature B cells. Production of FLCs occurs throughout the rest of B cell development and in plasma cells, in which secretion is highest. Tumors associated with the different stages of B cell maturation will secrete monoclonal FLCs into the serum, where they may be detected by FLC immunoassays (Box 1; Table 1).

Box1. Benefits of Serum Free Light-Chain Immunoassays

Table1. Assays for Free Light Chains

Production of FLCs in normal individuals is approximately 500 mg/day from bone marrow and lymph node cells. The molecules enter the blood and are readily partitioned between the intravascular and extravascular compartments. In normal individuals, serum FLCs are rapidly cleared and metabolized by the kidneys, depending on their molecular size.

Immunologic Testing

Traditionally, laboratories have detected the monoclonal immunoglobulins by protein electrophoresis, which began in the 1930s, and have characterized the proteins by immunofixation electrophoresis (IFE), which was developed in the 1980s.

The identification of κ and λ molecules has been accomplished with the use of antibodies specific for each type of protein. Immunodiffusion was initially used, followed by immunoelectrophoresis (in 1953), radial immunodiffusion, and ultimately nephelometry and turbidimetry. An auto mated nephelometric assay, described in 2001, represented a major breakthrough. This methodology allows for the quantitation of both κ and λ free light chains and can be performed using automated chemistry analyzers (e.g., Dade Behring [now Siemens AG], Beckman Coulter, Roche Hitachi, Olympus).

Each monoclonal protein (M protein or paraprotein) con sists of two heavy-chain polypeptides of the same class and subclass and two light-chain polypeptides of the same type. The different monoclonal proteins are designated by capital letters corresponding to the class of their heavy chains, which are designated by Greek letters: gamma (γ) in IgG, alpha (α) in IgA, mu (µ) in IgM, delta (δ) in IgD, and epsilon (ε) in IgE. The subclasses are IgG1, IgG2, IgG, and IgG4, or IgA1 and IgA2, and their light-chain types are κ and λ. A monoclonal protein is characterized by a narrow peak or localized band on electrophoresis, by a thickened bowed arc on immunoelectrophoresis, and by a localized band on immunofixation. Many different entities are associated with M proteins (monoclonal gammopathies; Box 2).

Box2. Monoclonal Gammopathies

Electrophoresis of the serum or urine reveals a tall sharp peak on the densitometer tracing or a dense localized band in most cases of multiple myeloma (Fig. 2). A monoclonal protein is demonstrable in the serum and urine in 90% of patients. In all, 60% of patients exhibit IgG, 20% IgA, 10% light chain only (BJ proteinemia), and 1% IgD. Electrophoresis of urine shows a globulin peak in 75% of cases, mainly albumin in 10% of patients, and a normal pattern in 15%. When an M spike is observed on serum protein electrophoresis, the suggested sequence of testing includes testing by immunoelectrophoresis and immunofixation (Table 2). Screening for cryoglobulins and viscosity may also be warranted.

Fig2. Serum electrophoretic patterns.  A, Normal patient.  B, Patient with multiple myeloma. C, Patient with Waldenström’s  macroglobulinemia.

Table2. Suggested Sequence of Immunologic Testing for Monoclonal Proteins

Immunoelectrophoresis, also called gamma globulin electrophoresis or immunoglobulin electrophoresis, is a method of determining the blood levels of three major immunoglobulins—IgM, IgG, and IgA—based on their combined electro phoretic and immunologic properties. Immunoelectrophoresis is also used frequently to diagnose MM, which affects the bone marrow. Drugs that may cause increased immunoglobulin levels include therapeutic gamma globulin, hydralazine, isoniazid, phenytoin (Dilantin), procainamide, oral contraceptives, methadone, steroids, and tetanus toxoid and antitoxin. The laboratory should be notified if the patient has received any vaccinations or immunizations in the 6 months before the test. Prior immunizations lead to increased immunoglobulin levels, resulting in false-positive results.

Because immunoelectrophoresis is not quantitative, it is being replaced by immunofixation, which is more sensitive and easier to interpret.

اخر الاخبار

اخبار العتبة العباسية المقدسة

وفد العتبة العباسية المقدسة يجري جولة في أروقة معرض بغداد الدولي للكتاب

شعبة التوجيه الديني النسوي تطلق برنامجًا قرآنيًّا لزائرات مرقد أبي الفضل العباس (عليه السلام)

جامعة الكفيل تطلق دورة تدريبية عن تقييم الأداء الجامعي لعدد من ملاكاتها

المجمع العلمي يقيم محفلًا قرآنيًا بذكرى ولادة الصادقين (صلوات الله عليهما)

المزيد

الآخبار الصحية

هل يتنبأ الذكاء الاصطناعي بأمراضنا قبل حدوثها؟

وداعا للنظارات.. قطرة عين واحدة قد تغير كل شيء ؟

دراسة تكشف تأثير "تيك توك" وتطبيقات الفيديو على سلوك الأطفال

"أسرار خفية" في الشاي الأخضر.. تغير قواعد الصحة والوزن

المزيد

الآخبار التكنلوجية

أول قطار يعمل بالهيدروجين في أميركا يدخل الخدمة رسميًا

أجهزة أبل القادمة.. "حصن منيع" في عصر الهجمات الرقمية !

روسيا: تطلق قمرين اصطناعيين بواسطة الصاروخ سويوز 2.1

ميزة ثورية.. أبل تدخل عالم قياس ضغط الدم

المزيد

مواضيع ذات صلة

Signs and Symptoms of Multiple myeloma

Pathophysiology of Multiple myeloma

CANCER

العوامل البيئية المسببة للسرطان

الأورام الصماوية للبنكرياس

متلازمة الأورام الغدية الصماوية المتعددة Multiple Endocrine Neoplasia (MEN) Syndrome

خصائص الخلايا السرطانية

Testicular germ cell tumours

Prostate carcinoma

Renal cell carcinoma

المسببات الكيميائية للسرطان chemical causes of cancer

الوراثة والسرطان Genes associated with cancer